Method of manufacturing a photodiode

Abstract

In a light receiving element and a semiconductor device manufacturing method, the low density PN junction is formed by constructing the internal composition of the photodiode with N + type diffusion layer, N − type epitaxial layer, P − type epitaxial layer, P + type deposit layer, and P type Si from the light receiving surface, the vacant layer to be occurred when the photodiode is reverse biased will be widened and the light receiving sensitivity and the frequency characteristic will be improved. Furthermore, since the separation of bipolar elements will be conducted by P − epitaxial layer, the efficiency in density control at the time of P − type epitaxial growth can be improved.

What is claimed is:  
     
       1. A method of manufacturing a semiconductor device having both a light receiving element and a bipolar element, the method comprising the steps of: 
       providing a first conductive type semiconductor substrate for both the light receiving element and the bipolar element;  
       forming a first conductive type semiconductor layer having an impurity density which is greater than an impurity density of the first conductive type semiconductor substrate on substantially all of the substrate in the light receiving element only;  
       forming a first conductive type epitaxial layer having an impurity density which is less than the impurity density of the first conductive type semiconductor layer over both the first conductive type semiconductor layer in the light receiving element and the substrate in the bipolar element, wherein the first conductive type semiconductor layer is formed between the first conductive type semiconductor substrate and the first conductive type epitaxial layer;  
       forming a second conductive type semiconductor layer on a part of the first conductive type low density epitaxial layer in the bipolar element;  
       forming another first conductive type semiconductor layer on an isolation part of the bipolar element;  
       forming a second conductive type epitaxial layer having an impurity density which is less than the impurity density of the second conductive type semiconductor layer on each of the first conductive type epitaxial layer, the second conductive type semiconductor layer, and the first conductive type semiconductor layer on the isolation part of the bipolar element; and  
       forming a second conductive type diffusion layer having an impurity density which is greater than the impurity density of the second conductive type epitaxial layer on the second conductive type epitaxial layer in the light receiving element only.  
     
     
       2. A method of manufacturing a semiconductor device having both a light receiving element and a bipolar element, the method comprising the steps of: 
       providing a first conductive type semiconductor substrate for both the light receiving element and the bipolar element;  
       forming a first conductive type semiconductor layer having an impurity density which is greater than the impurity density of the first conductive type semiconductor substrate on substantially all of the substrate in the light receiving element only;  
       forming a first conductive type epitaxial layer having an impurity density which is less than the impurity density of the first conductive type semiconductor layer over both the first conductive type semiconductor layer in the light receiving element and the substrate in the bipolar element, wherein the first conductive type semiconductor layer is formed between the first conductive type semiconductor substrate and the first conductive type epitaxial layer;  
       forming a first conductive type second epitaxial layer having an impurity density which is less than the impurity density of the first conductive type epitaxial layer over the first conductive type epitaxial layer;  
       forming a second conductive type semiconductor layer on a part of the first conductive type epitaxial layer in the bipolar element;  
       forming another first conductive type semiconductor layer on an isolation part of the bipolar element;  
       forming a second conductive type epitaxial layer having an impurity density which is less than the impurity density of the second conductive type semiconductor layer on each of the first conductive type epitaxial layer, the second conductive type semiconductor layer, and the first conductive type semiconductor layer on an isolation part of the bipolar element; and  
       forming a second conductive type diffusion layer having an impurity density which is greater than the impurity density of the second conductive type epitaxial layer on the second conductive type eptiaxial layer in the light receiving element only.